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Background Vitamin D status is associated with muscle strength and maintenance of muscle fibers. However, which serum vitamin D biomarker better reflects sarcopenia remains unclear. The aim of this study was to investigate associations between various serum vitamin D biomarkers (total 25‐hydroxy vitamin D [25(OH)D], bioavailable 25(OH)D, 24,25‐dihydroxyvitamin D [24,25(OH)2D], and vitamin D metabolite ratio [VMR]) and sarcopenia. Methods The data for 83 hip fracture patients were finally included in the analysis. Sarcopenia was defined according to the Asia Working Group for Sarcopenia (AWGS) criteria. Measurements of 24,25(OH)2D and 25(OH)D were made using solid‐phase extraction (SPE) and subsequent liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). Vitamin D binding protein (VDBP) concentration was measured using an enzyme‐linked immunosorbent assay. The VMR was calculated by dividing serum 24,25(OH)2D by serum 25(OH)D and then multiplying by 100. Based on total 25(OH)D, VDBP, and albumin concentrations, bioavailable 25(OH)D concentrations were calculated using the equations from the other previous studies. Results Bioavailable 25(OH)D levels were significantly (p = 0.030) decreased in the sarcopenia group compared with the non‐sarcopenia group. Results of ROC analysis for the diagnosis of sarcopenia using serum level of bioavailable of 25(OH)D revealed that the cutoff point for bioavailable 25(OH)D was 1.70 ng/ml (AUC = 0.649, p < 0.001). In the group with a bioavailable 25(OH)D less than 1.70 ng/ml, the incidence of sarcopenia increased by 3.3 times (odds ratio: 3.33, p = 0.013). Conclusion We demonstrated that bioavailable 25(OH)D was associated with sarcopenia among the various serum vitamin D biomarkers. Bioavailable vitamin D might be helpful for assessing the risk of sarcopenia. We demonstrated that bioavailable 25(OH)D was associated with sarcopenia among the various serum vitamin D biomarkers. Bioavailable vitamin D might be helpful for assessing the risk of sarcopenia.

Background: Vitamin D deficiency in early childhood is commonly defined using fixed 25(OH)D thresholds, most often <20 ng/mL. However, inclusion of the C3-epimer (3-epi-25(OH)D3) in total 25(OH)D measurements may influence classification, particularly in children with borderline concentrations. Methods: In this cross-sectional study of 128 children aged 0–36 months, vitamin D metabolites were quantified using LC–MS/MS in dried blood spot (DBS) samples. Vitamin D deficiency was defined as <20 ng/mL. Total 25(OH)D was recalculated after subtraction of the C3-epimer to assess changes in deficiency classification. Agreement was evaluated using Cohen’s κ, and systematic differences were tested with McNemar’s test. Diagnostic performance parameters were calculated using epimer-resolved 25(OH)D as the reference standard. Results: Mean 25(OH)D3 concentration was 20.3 ± 6.2 ng/mL, and 57% of children were classified as deficient. After epimer subtraction, deficiency classification changed in 22 of 128 children (17.2%). Agreement between classifications was substantial (κ = 0.67), but McNemar’s test demonstrated a significant systematic shift (p < 0.001). Sensitivity of total 25(OH)D including the epimer for detecting deficiency was 70.3% (95% CI: 59.0–80.0%), with specificity of 100% (95% CI: 94.3–100%). Reclassification was strongly concentrated among children with borderline 25(OH)D3 concentrations (18–22 ng/mL), where 54.5% were reclassified compared with 4.2% outside this range. Reclassification was not associated with age. Conclusions: In young children, inclusion of the C3-epimer in total 25(OH)D measurement leads to potentially clinically relevant misclassification of vitamin D deficiency, particularly near diagnostic thresholds. Epimer-resolved assessment may improve diagnostic precision in cases with borderline vitamin D concentrations.

Background: The antibody reactivity against Epstein-Barr nuclear antigen-1 (EBNA-1), and 25-hydroxyvitamin D (25(OH)D) status have been associated with multiple sclerosis (MS) risk. Interaction between these two factors has been proposed. Objectives: The objective of this paper is to examine the association between antibody reactivity against EBNA-1 and five EBNA-1 domains, and the risk of MS, and to examine if these antibodies and 25(OH)D status interact regarding MS risk in prospectively collected blood samples. Methods: Antibody reactivity and 25(OH)D levels were measured using ELISAs in n = 192 MS cases and n = 384 matched controls. The risk of MS was analysed using matched logistic regression. Interaction on the additive scale was assessed. Results: The risk of MS increased across tertiles of antibody reactivity against EBNA-1, domain EBNA-1402–502, and domain EBNA-1385–420; p trends < 0.001. In young individuals (below median age at sampling, < 26.4 years), these associations were stronger, and 25(OH)D levels correlated inversely to antibody reactivity against EBNA-1 and the EBNA-1 domains. No statistical interaction was found. Conclusions: We confirm that increased antibody reactivity against EBNA-1 is a risk factor of MS. 25(OH)D status might influence the immune response towards Epstein-Barr virus in young subjects, and thereby modulate MS risk.

Objective : To evaluate the nutritional status of vitamin D in urban populations of healthy elderly people living at home, in different regions of Argentina. Design : Cross-sectional study. Subjects : In total, 386 ambulatory subjects over 65 y of age from seven cities (between latitude 26°S and 55°S) were asked to participate between the end of winter and the beginning of spring. Of these, 369 accepted, 30 were excluded because of medical history or abnormal biochemical determinations. Finally, 339 subjects (226 women and 113 men) ( X ±s.d.) (71.3± 5.2 y) were included. Results : Serum 25OHD levels were lowest in the South (latitude range: 41°S–55°S): 14.2±5.6 ng/ml ( P <0.0001 vs North and Mid regions); highest in the North (26°S–27°S): 20.7±7.4 ng/ml ( P <0.03 vs Mid, P <0.0001 vs South); and intermediate in the Mid region (33°S–34°S) 17.9±8.2 ng/ml. Serum mid-molecule PTH (mmPTH) and 25OHD were inversely related: ( r =−0.24, P <0.001). A cutoff level of 25OHD at which serum mmPTH levels began to increase was established at 27 ng/ml. A high prevalence (87–52%) of subjects with 25OHD levels in the deficiency-insufficiency range (25OHD levels <20 ng/ml) was detected. Conclusion : This study shows that vitamin D deficiency/insufficiency in the elderly is a worldwide problem. Correction of this deficit would have a positive impact on bone health of elderly people. Sponsorship : Asociación Argentina de Osteología y Metabolismo Mineral (AAOMM).

In animal studies, vitamin D supplementation has been shown to improve gut microbiota and intestinal inflammation. However, limited evidence exists on the effect of vitamin D supplementation on the human gut microbiota. We examined the effect of vitamin D supplementation on faecal microbiota in 26 vitamin D-deficient (25-hydroxyvitamin D (25(OH)D) ≤50 nmol/L), overweight or obese (BMI ≥25 kg/m2) otherwise healthy adults. Our study was ancillary to a community based double-blind randomised clinical trial, conducted between 2014 and 2016. The participants provided stool samples at baseline and after 100,000 international units (IU) loading dose of cholecalciferol followed by 4000 IU daily or matching placebo for 16 weeks. Faecal microbiota was analysed using 16S rRNA sequencing; V6–8 region. There was no significant difference in microbiome α-diversity between vitamin D and placebo groups at baseline and follow-up (all p > 0.05). In addition, no clustering was found based on vitamin D supplementation at follow-up (p = 0.3). However, there was a significant association between community composition and vitamin D supplementation at the genus level (p = 0.04). The vitamin D group had a higher abundance of genus Lachnospira, and lower abundance of genus Blautia (linear discriminate analysis >3.0). Moreover, individuals with 25(OH)D >75 nmol/L had a higher abundance of genus Coprococcus and lower abundance of genus Ruminococcus compared to those with 25(OH)D <50 nmol/L. Our findings suggest that vitamin D supplementation has some distinct effects on faecal microbiota. Future studies need to explore whether these effects would translate into improved clinical outcomes.

Group-specific component (GC) subtyping was performed by isoelectric focusing in 318 Spanish drug users at risk for infection or infected by HIV (85 HIV seronegatives, 111 HIV seropositives without symptoms, 89 seropositives with symptoms, 33 AIDS patients) and 187 healthy individuals. There was no significant association between GC subtypes and susceptibility to HIV infection and/or progression to AIDS.

The frequencies of group-specific component (GC) subtypes were studied in a population of 4,053 conscripts and blood donors from the counties of Vasterbotten and Norrbotten in northern Sweden. The individuals were distributed according to place of birth into 23 subpopulations. A significant heterogeneity between the 23 regions was observed for the GC*1F, GC*1S and GC*2 genes, and clines were found for all genes. The frequecy of the GC*1F gene was increasing in the northern direction, and the frequencies of the GS*1S and GC*2 genes were increasing in the southern direction. The geographical pattern of the GC*1F gene frequency could be explained in terms of Lappish influence.

There is conflicting evidence about the relationship between vitamin D deficiency and depression, and a systematic assessment of the literature has not been available. To determine the relationship, if any, between vitamin D deficiency and depression. A systematic review and meta-analysis of observational studies and randomised controlled trials was conducted. One case-control study, ten cross-sectional studies and three cohort studies with a total of 31 424 participants were analysed. Lower vitamin D levels were found in people with depression compared with controls (SMD = 0.60, 95% CI 0.23-0.97) and there was an increased odds ratio of depression for the lowest v. highest vitamin D categories in the cross-sectional studies (OR = 1.31, 95% CI 1.0-1.71). The cohort studies showed a significantly increased hazard ratio of depression for the lowest v. highest vitamin D categories (HR = 2.21, 95% CI 1.40-3.49). Our analyses are consistent with the hypothesis that low vitamin D concentration is associated with depression, and highlight the need for randomised controlled trials of vitamin D for the prevention and treatment of depression to determine whether this association is causal.

The Tf and Gc polymorphic subtype variants have been examined by means of isoelectric focusing in a population sample from two subpyrenean regions in the province of Gerona (Northeast Spain). The estimated allele frequencies were Tf*C1 = 0.774, Tf*C2 = 0.167, TF*C3 = 0.055, TF*B = 0.004; Gc*1F = 0.129, Gc*1S = 0.555 and Gc*2 = 0.316. These values are in general similar to those so far reported in other Spanish populations. The comparisons between our data and those published in Spain, indicate that the present sample is closer to Barcelona than to the other groups compared. Die polymorphen Tf und Gc Subtype-Varianten wurden mit Hilfe der Isoelektrofokussierung an einer Populationsstichprobe aus zwei Regionen der Sub-Pyrenäen im Gebiet der Provinz Gerona (Nordost-Spanien) bestimmt. Die geschätzten Allelenfrequenzen lauten: Tf*C1 = 0.774, Tf*C2 = 0.167, Tf*C3 = 0.055, Tf*B = 0.004; Gc*1F = 0.129, Gc1S = 0.555 und Gc*2 = 0.316. Diese Werte entsprechen im wesentlichen den bisher für spanische Populationen mitgeteilten. Vergleiche unserer Daten mit anderen spanischen zeigen, daß unsere Stichprobe einer aus Barcelona näher steht als anderen spanischen Populationsstichproben.